Scientists at the giant European particle physics laboratory, Cern, are in last minute discussions over closing their largest particle collider.

The massive machine, which is due to be replaced with a new one, may be on the brink of spotting one of the most sought after prizes in physics: the Higgs boson, which explains why all other particles have mass.

Researchers were due to decommission the old machine and build a more powerful accelerator but they granted it a short reprieve for follow-up experiments in September.

A final decision will be made on Friday over whether to close the machine for good or start running experiments again next year.

'Shadow' of Higgs

A spokesperson for Cern said experiments at the Large Electron-Positron (Lep) collider were still detecting a handful of events that may indicate the fleeting appearance of the Higgs boson.

"The effect has not gone away," he told BBC News Online. "We need an enormous amount of data to make it absolutely certain - to get this data we would have to run the Lep for several more months.

"The answer lies in the physics," he added. "On Friday, we will examine the physics results and until we have these results and these results have been analysed, no decision to continue the Lep will be made."

The collider is hidden in a 27-km (17-mile), circular tunnel near Geneva. Tiny particles are made to race through the tunnel at velocities close to the speed of light and then smash into each other.

Subatomic debris

Examining the debris from these collisions reveals the inner workings of atoms and gives scientists clues to the properties of matter. Researchers say finding the Higgs boson is vital to our understanding of the way the Universe is made because it can explain why matter has mass.

Physicists think the Higgs gives rise to a field through which all other subatomic particles, such as quarks, gluons, photons and electrons, must pass.

As they interact with the field, the particles experience a drag - the more drag, the greater the mass; the less drag, the lighter the particle. Scientists cannot see the field but they could infer its existence if they can find the particle associated with it in the subatomic debris that is produced when matter is smashed together at high energies in an accelerator like the Lep

Cern's US rival, Fermilab near Chicago, is also intensifying its efforts to find the Higgs. According to commentators, the team that finds the particle is almost guaranteed a Nobel Prize.